Hi there. It is not really a DIY fix, unless you’ve got a replacement OSS to swap in, and/or have experience of such systems. I’m saying this based on what I read on the issue 6 or 7 years ago when I had mine.
I was so tempted to fix the one I had on mine, and glad to this day I didn’t tackle it to be honest.
Plenty to read on A2OC about the system, and methods of repair;
https://www.a2oc.net/community/index...-repair.36530/
Enjoy the A2!